CM Coup ler Balance
1.
Connect the inline wattmeter with 50-ohm
dummy load to the ANT A jack, and set the
FC-757AT and transceiver to the 14 MHz
band. On the FC-757AT,press the ANTENNA
A button, and set the THRU switch to the
depressed position and the SWR/PO switch
to the SWR (depressed) position.
2.
Adjust the transmitter to provide 1 OOW
steady CW, and then with the PTT line closed
'
adjust TC301 (rear left corner of the chassis)
for minimum deflection on the FC-757AT
meter.
This procedure must be repeated after the PO
Meter and SWR Meter alignments have been
performed.
PO Meter Calibration
1.
First perform the previous CM Coupler
Balance procedure.
2.
Set the SWR/PO switch to the PO (un
depressed) position, and with the METER
15/150 switch in the 150 (undepressed)
position, key the transmitter and adjust
VR104 on the CPU Unit so that the power
indications on the internal and external watt
meters coincide at 100 watts.
3.
Release the PTT switch and change the scale
of the external wattmeter to the lower range.
Press the 15/150
button to change the
internal wattmeter to the 15-watt range.
Reduce the transmitter power to 10 watts,
and then key the transmitter and adjust
VR103 on the CPU Unit so that the power
indications on both meters again agree, at 10
watts.
SWR Meter Calibration
The CM Coupler Balance and PO Meter alignment
procedures must be performed before proceeding.
1.
Note the required settings on the transmitter
to produce 10 watts and 100 watts output
into 50 ohms, and then replace the 50-ohm
load with the 17-ohm dummy load.
2.
Preset VR101 on the CPU Unit fully counter
clockwise, and VR,02 fully clockwise. Set the
METER SWR/PO switch to the SWR posi
tion, and the 15/ 150 switch to the 150 posi
tion. Set the transmitter controls to the 100-
watt positions (determined in the previous
step).
3.
Key the transmitter and adjust VR101 clock
wise just to the threshold point where the
SWR meter indication begins to decrease.
Then adjust VR102 so that the meter indicates
exactly 3 (-to-1 ).
4.
Now reduce the transmitter power to the 10-
watt positions, and check that the SWR meter
indication is near 3. If it has changed much,
carefully readjust VR10
1
for the threshold
point, and VR102 for the midscale deflection.
Repeat the adjustments at 100 and 1 O watts
until the indicated SWR, when set to 3 at 100
watts, is between
2
and 3.3 (10 and 25 on the
�
SOW PO scale) at 10 watts. If necessary,
increase power to 15 or
20
watts for the low
power check.
5.
Repeat the CM Coupler Balance procedure.
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Содержание FC-757AT
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